Outdoor-indoor air pollution in urban environment: challenges and opportunity

With the continual improvement in our quality of life, indoor air quality has become an important area of concern in the twenty-first century. Indoor air quality is affected by many factors including the type and running conditions of indoor pollution sources, ventilation conditions, as well as indoor activities. Studies revealed that the outdoor environment is also an important factor that cannot be neglected for indoor air quality studies. In this review, the indoor and outdoor air pollution relationships obtained from different studies are discussed in order to identify the key factors affecting the indoor air quality. As climate change is recognized as imposing impacts on the environment, how it affects the indoor air quality and the health impacts to the occupants will be evaluated in this paper. The major challenges and opportunities in indoor/outdoor air pollution studies will be highlighted.published_or_final_versio

Life cycle analysis for petroleum fuels and renewable Jet fuels

Session VII - Energy Optimization II: no. 6At the time when the use of fossil fuel means ever increasing energy scarcity and environmental crisis in the world we live, we need greener innovations now more than ever. Growing attention has been drawn to biofuels such as ethanol and biodiesel and they have gradually taken up a certain amount of the total energy supply. Despite preferential development of them, environmental and ecological uncertainties still exist. Life cycle analysis (LCA), with deliberate system boundaries and life cycle inventories, has been applied by scientific literatures to calculate two principal functional units, the energy efficiency and GHG balance, from cradle to grave of different renewable ...postprin

On the heating environment in street canyon

This study investigates the impact of building aspect ratio (building-height-to-street-canyon-width-ratio), wind speed and surface and air-temperature difference (Δθs-a) on the heating environment within street canyon. The Reynolds-averaged Navier-Stokes (RANS) and energy transport equations were solved with Renormalization group (RNG) theory version of k-turbulence model. The validation process demonstrated that the model could be trusted for simulating air-temperature and velocity trends. The temperature and velocity patterns were discussed in idealized street canyons of different aspect ratios (0.5-2.0) with varying ambient wind speeds (0.5-1.5 m/s) and Δθs-a (2-8 K). Results show that air-temperatures are directly proportional to bulk Richardson number (Rb) for all but ground heating situation. Conversely, air-temperatures increase significantly across the street canyon with a decrease in ambient wind speed; however, the impact of Δθs-a was negligible. Clearly, ambient wind speed decreases significantly as it passes over higher AR street canyons. Notably, air-temperatures were the highest when the windward wall was heated and the least during ground heating. Conversely, air-temperatures were lower along the windward side but higher within the street canyon when the windward wall was heated. © 2010 The Author(s).published_or_final_versionSpringer Open Choice, 21 Feb 201

Technology development in nano-sized photocatalyst powder preparation technologies

Nano-sized semiconductor powders for use as photocatalysts have great potential in environmental and energy engineering applications. The photocatalytic activity of photocatalyst is significantly affected by preparation process since the crystalline structure of photocatalyst is dependent on preparation conditions. This paper aims to give an overview of the research progress of nano-sized photocatalyst powder preparation technologies, including solid route, gas phase route, and liquid route. The advantages and disadvantages of different preparation technologies are analyzed and compared. The research direction and prospect of photocatalyst preparation method is analyzed.纳米半导体材料作为光催化剂在环境、能源领域具有广阔的应用前景。光催化剂的制备过程对催化剂的晶体结构有重要的影响,从而影响其光催化活性。本文较系统地综述了国内外对光催化剂纳米粉体制备的研究进展,包括固相法、气相法和湿化学法。对比分析了各种制备技术的优缺点,并对今后的研究方向和应用前景进行了分析。link_to_subscribed_fulltextpublished_or_final_versio

A high specific capacity membraneless aluminum-air cell operated with an inorganic/organic hybrid electrolyte

Aluminum-air cells have attracted a lot of interests because they have the highest volumetric capacity density in theory among the different metal-air systems. To overcome the self-discharge issue of aluminum, a microfluidic aluminum-air cell working with KOH methanol-based anolyte was developed in this work. A specific capacity up to 2507 mAh g¯¹ (that is, 84.1% of the theoretical value) was achieved experimentally. The KOH concentration and water content in the methanol-based anolyte were found to have direct influence on the cell performance. A possible mechanism of the aluminum reactions in KOH methanol-based electrolyte was proposed to explain the observed phenomenon

Orthogonal array design for biodiesel production optimization: using ultrasonic-assisted transestification of Camelina sativa L. Crantz oil

Bioenergy Technology (BE): 0234Camelina seed oil has recently attracted great interest as a low-cost feedstock for biodiesel production because of its high oil content and environmental benefits. In the present study, an orthogonal array design was used to optimize the biodiesel production from camelina seed oil using ultrasonic-assisted transesterification. Four relevant factors are investigated: methanol to oil ratio, catalyst concentration, reaction time and temperature to obtain maximum fatty acid methyl ester (FAME) yield of biodiesel. An OA25 matrix was employed to study the effect of the four factors, by which the effect of each factor was estimated using statistical analysis. Based on the results of the statistical analysis after the orthogonal experiments, maximal biodiesel FAME yield (98.6 %) was obtained under the conditions of 8:1 methanol to oil molar ratio, 1.25 wt.% catalyst concentration (KOH), 50 min reaction time, and 55 ℃ reaction temperature. Other properties of the optimized biodiesel, including density, kinematic viscosity, and acid value, were conformed to the relevant ASTM and EN biodiesel standards and thus the optimized biodiesel from camelina oil basically qualified to be used as diesel fuel.published_or_final_versionThe World Renewable Energy Congress (WREC 2011), Linköping, Sweden, 8-13 May 2011. In Linköping Electronic Conference Proceedings, 2011, ECP57, v. 1, p. 79-8

Large-eddy simulation of turbulent transports in urban street canyons in different thermal stabilities

Three scenarios of large-eddy simulation (LES) were performed to examine the characteristic flow and pollutant dispersion in urban street canyons under neutral, unstable and stable thermal stratifications. Street canyons of unity aspect ratio with ground-heating or –cooling are considered. In the LESs of the thermal stabilities tested, a large primary recirculation is developed in the center core and the turbulence production is dominated at the roof level of the street canyon. The current LES results demonstrate that unstable stratification enhances the mean wind, turbulence and pollutant removal of street canyons. On the other hand, in stable stratification, which has been less investigated in the past, the ground-level mean wind and turbulence are substantially suppressed by the large temperature inversion. Whereas, the weakened recirculating wind in the street canyon results in a larger velocity gradient that increases the turbulence production at the roof level. It also slows down the turbulence being carried from the roof down to the lower street canyon. Therefore, a higher level of turbulent kinetic energy (TKE) is retained at the mid-level of the windward side in the stably stratified street canyon.postprintThe 5th International Symposium on Computational Wind Engineering (CWE2010), Chapel Hill, N.C., 23-27 May 2010

Plasma-driven catalysis process for toluene abatement: Effect of water vapor

Plasma-driven catalysis (PDC) was used to remove toluene in air. Water vapor is a critical operating parameter in this process. Its effect on toluene removal efficiency, carbon balance, CO 2 selectivity, and outlet O 3 concentration was systematically investigated. Results showed that water vapor imposed negative effect on toluene decomposition since it depressed the formation and catalytic decomposition of O 3. Water vapor deposited on the catalyst would cover the catalytic active sites, resulting in the deactivation of the catalyst. There was an optimum water vapor content for the highest carbon balance and CO 2 selectivity. The present paper sheds some insight into the effect of water vapor and provides a valuable basis for the application of the PDC technology. © 2010 IEEE.published_or_final_versio

Abatement of toluene in the plasma-driven catalysis: Mechanism and reaction kinetics

The mechanism and reaction kinetics of toluene destruction in a plasma-driven catalysis (PDC) system were studied. The results show that the toluene removal efficiency (TRE) is greatly increased while the level of O 3 by-product is significantly reduced in PDC as compared with that in nonthermal plasma (NTP). The rate constant of toluene destruction in the PDC is more than twice than that in NTP. Among the multiple reactive species responsible for toluene destruction in the PDC, hydroxyl radicals (̇OH) had a small contribution, whereas energetic electrons and atomic oxygen (O) were the most important. The enhanced performance of toluene destruction by PDC was mainly due to greater amounts of O formed during the process. The catalysts improved toluene destruction by catalytic decomposition of O 3 and generation of O. Essentially, better toluene abatement can be achieved by focusing on the increased energy density and improved performance of the catalyst for O 3 decomposition. © 2006 IEEE.published_or_final_versio

In situ photogalvanic acceleration of optofluidic kinetics: a new paradigm for advanced photocatalytic technologies

A multiscale-designed optofluidic reactor is demonstrated in this work, featuring an overall reaction rate constant of 1.32 s¯¹ for photocatalytic decolourization of methylene blue, which is an order of magnitude higher as compared to literature records. A novel performance-enhancement mechanism of microscale in situ photogalvanic acceleration was found to be the main reason for the superior optofluidic performance in the photocatalytic degradation of dyes as a model reaction